Abstract

A crystal of Na₃Li₃Ga₂F₁₂:Cr 4.5-mm thick was pumped with a krypton-ion laser operating at 647 nm. The sample was pumped longitudinally in a nearly concentric cavity and exhibited free lasing at 791 nm. With a birefringent element in the cavity, the material tuned continuously from 741 to 841 nm. A slope efficiency of 14.5% was measured with 4.5% output coupling. Experiments using a modified Findlay-Clay¹ technique indicated relatively low resonator loss levels of the order of 0.5% for wavelengths ranging from 780 to 820 nm. However, the measured gain was several times smaller than might be expected. At 790 nm the measured round-trip resonator gain per unit absorbed pump power was 3.5% W^-1. This was nearly a factor of 3 lower than the gain estimated using the cross section for stimulated emission based on the (assumed) purely radiative room temperature fluorescence lifetime of 330 μs. Possible causes for the gain reduction include nonradiative losses and excited state absorption.

© 1986 Optical Society of America